Adam Clarke, on Neh 11:23

“For the king’s commandment was concerning them, and an order among the singing men day by day.”

“It was the king's commandment - By the king some understand David, and others Artaxerxes. It is most probable that it was the latter; who wished that a provision should be made for these, a part of whose office was to offer up prayers also, as well as praises. For we know that Darius made an ample provision for the priests, that they might offer sacrifices of sweet savor unto the God of heaven; and pray for the life of the king and of his sons, Ezr 6:10. Some have thought that they had been Jewish singers employed in the service of the Persian king, to whom he had given a salary, and to whom he wished still to continue the same.”

Imported from an open dataset — not yet checked against the printed edition.